A seat belt assembly for a vehicle that includes an anchor portion having an anchor bolt adapted to attach to a vehicle. A seat belt web is associated with the anchor portion. A sheath member is coupled to the anchor portion with the sheath member having opposing top and bottom surfaces and opposing side surfaces. The opposing top and bottom surfaces and opposing side surfaces define an interior cavity. The sheath member includes a plurality of detents formed on the opposing side surfaces. An extension plate having opposing proximal and distal ends as well as opposing top and bottom surfaces bounded by opposing lateral edges is slidingly disposed within the interior cavity of the sheath member. The extension plate includes a pair of arms formed on the opposing lateral edges. An extension arm formed about the extension plate includes first and second ends with the first end coupled to the proximal end of the extension plate. The second end of the extension arm includes a web guide formed on an end. The pair of arms releasably engage the plurality of detents for telescopic adjustment of the extension arm whereby the web guide is movable to a plurality of positions.